WASHINGTON (Reuters) - U.S. senators signaled on Wednesday a new willingness to consider restrictions on the sale of guns after the Orlando nightclub massacre, with presumptive Republican presidential nominee Donald Trump and others in his party ready to discuss limited gun control measures.

With Republicans and the National Rifle Association gun lobby under pressure to respond to the worst mass shooting in modern U.S. history, Trump said he would meet with the NRA to discuss ways to block people on terrorism watch or no-fly lists from buying guns.

Emotions have run high in Congress since Sunday's mass shooting with Democrats stalling Senate proceedings on Wednesday in a bid to push for tougher gun control legislation. Democratic senators planned to speak on the Senate floor well into Wednesday night.

The Senate began discussions on legislation to ban firearm sales to the hundreds of thousands of people on U.S. terrorism watch lists after a gunman who had been on such a list killed 49 people at a gay nightclub on Sunday.

But following a full day of wrangling, Senate Democratic leader Harry Reid said that negotiations "were little more than a smokescreen by Republicans trying to give themselves political cover while they continue to march in lock-step with the NRA's extreme positions."

Reid said there were no Republican proposals "that come close to attracting Democratic support."

Earlier on Wednesday, Republican Senate Majority Leader Mitch McConnell urged senators to offer ideas on how to prevent another attack like the one in Orlando.

“I do not believe this was some random act of violence," McConnell said. "It seems clear this was cold-blooded murder committed by a terrorist who picked his targets with deliberate malice." On Tuesday, McConnell said that "nobody wants terrorists to have firearms."

Earlier in the week, some Democrats in the House of Representatives interrupted a moment of silence for the victims, with shouts of "Where's the bill?" to protest the Republican-led chamber's refusal to consider tougher gun laws.

If Congress was to pass a gun control measure, it would mark the first time in more than 20 years that lawmakers agreed on how to address the hot-button issue. A ban on semi-automatic assault weapons, such as the one used in Orlando, had gone into effect in 1994 and expired 10 years later.

Republicans over the years have blocked gun control measures saying they step on Americans' right to bear arms as guaranteed under the U.S. Constitution.

Senator John Cornyn, the No. 2 Senate Republican, confirmed that he and Democratic Senator Dianne Feinstein were holding private talks on a possible compromise bill stopping weapons sales to those on watch lists.

OPPORTUNITY CITED

Another Republican, Senator Pat Toomey of Pennsylvania, also is working on a bill that would keep guns from people on watch lists, a gun control group said.

Toomey, who is in a possibly difficult re-election bid this year, took to the Senate floor urging compromise.

“So there’s an obvious opportunity here guys, to work together and find a solution,” he said, adding, "This is not rocket science to figure this out."

A spokeswoman for Toomey, E.R. Anderson, said the senator was seeking bipartisan support for an approach that he had tentatively agreed on with gun control group Everytown for Gun Safety, which is backed by ex-New York Mayor Michael Bloomberg.

Everytown spokeswoman Erika Lamb said the group was encouraged by the discussions but added, "We are not there yet and our support for any compromise legislation is contingent on support from both Republicans and Democrats."

Toomey's bill would allow the U.S. attorney general to create a new list of "likely terrorists" and block any person on the list from buying or selling a gun. If someone was denied a gun, he or she would be entitled to a swift court hearing where the attorney general would have to turn over the evidence against the person.

Democrats were dubious. One problem, a Democratic aide said, was that under the proposal officials would just have three days to try to block sales to anyone not already on the new list.

Congressional Republicans and the NRA have thwarted previous gun control measures backed by President Barack Obama and other Democrats after other mass shootings, and supporters of new restrictions remained cautious about the moves.

"The Cornyn bill is outlandish and is worse than nothing. From what I'm told all of the compromises proposed by Cornyn and Toomey are not at all acceptable," said Senator Chuck Schumer, a Democrat of New York.

Feinstein, speaking to reporters following a closed briefing from the Obama administration on the Orlando massacre, held out little hope her talks with Cornyn would bear fruit. "I don't think it's going to work out," she said, but added she was still engaged in talks.

NRA HAPPY TO MEET WITH TRUMP

Trump said on Twitter he would meet with the NRA "about not allowing people on the terrorist watch list, or the no-fly list, to buy guns." His campaign did not specify what he might support legislatively, and a spokeswoman declined to give details about the timing or nature of the meeting.

The NRA, a politically influential lobbying group that claims more than 4 million members, said in a statement it was "happy to meet" with Trump, whom it endorsed for president on May 20.

The group said in a statement that anyone on a terrorism watch list who tries to buy a gun "should be thoroughly investigated" by the Federal Bureau of Investigation and any sale to that person delayed, a position the lobby group has long held.

Presumptive Democratic presidential nominee Hillary Clinton, who has supported gun control efforts, on Monday said she was "bewildered" that Republicans in Congress in December had blocked a Democratic effort to restrict gun sales to people on the watch lists.

The U.S. government maintains two terrorism watch lists: a no-fly list barring people from flying to and from the United States and a larger one that subjects travelers to greater scrutiny at airports and border crossings.

An FBI official said in 2014 there were 64,000 people on the no-fly list and 800,000 on the broader list. The Orlando gunman, Omar Mateen, the U.S.-born son of Afghan immigrants, was on the broader list at one time.

NRA Executive Director Chris Cox also voiced backing for legislation offered in December by Cornyn, who proposed to put gun sales on hold for 72 hours for people on watch lists. Critics have said such background checks could take longer to complete.

White House spokesman Josh Earnest said it was too soon to tell if Republicans would support "common sense" steps like blocking firearm sales to people on the no-fly lists.